1. Field of the Invention
The present invention relates generally to the distribution of power in an automated data storage system.
2. Background Art
Current automated libraries for tape cartridges typically include arrays of multiple storage cells housing the tape cartridges, as well as multiple media drives. Multiple automated robotic devices may be used to move tape cartridges between the various storage cells and media drives within a library.
The use of multiple robotic devices in automated tape cartridge libraries raises various problems concerning the distribution of power to such robotic devices. More particularly, robotic devices used in automated tape cartridge libraries require power for operation thereof. In prior art automated tape cartridge libraries, the movement of the robotic devices is restricted by wire cable connections used for providing such power. That is, such cabling can prevent the robotic devices from crossing paths, or from continuous movement in one direction around the library without the necessity of ultimately reversing direction.
Power cabling can be eliminated through the use of conductors running along tracks which support the robotic devices. Brushes on the robotic devices contact the conductors to supply power to the robotic devices. Alternatively, brushes may be part of a pickup assembly for supplying power to the robotic devices. For example, wheels may contact the conductors with brushes contacting the wheels.
The effects of use and age can cause brushes to wear down or otherwise degrade, resulting in reduced performance or failure of the robotic device. What is needed is to detect brush failure so that the defective brush can be replaced. Preferably, failure detection of brushes should occur in a manner which permits the robotic device to continue operating until such time as the defective brush can be easily repaired.
Brush failure detection is accomplished through the use of two brushes drawing power from the same conductor.
A method of detecting brush failure for a robotic device traveling along at least one rail associated with a data storage library is provided. The rail includes a first conductor and a second conductor for supplying power to the robotic device. Current is sensed through each of a first brush and a second brush passing current between the first conductor and the robotic device. Similarly, current is sensed through each of a third brush and a fourth brush passing current between the second conductor and the robotic device. At least one motor is driven with at least one of a first current and a second current from the first and second brushes, respectively, and at least one of a third current and a fourth current from the third and fourth brushes, respectively. The motor propels the robotic device along the rail permitting access to a plurality of data storage media devices, such as cartridges, cassettes, media packages, media access equipment, identification devices, access ports and the like, held within the library. A failure of at least one of the brushes is determined by sensing the first current, second current, third current and fourth current.
In embodiments of the present invention, failure is determined based on the difference between the first current and the second current or the difference between the third current and the fourth current. The first brush and second brush may be spaced apart along the first conductor in the direction of travel of the robotic device. The first and second brush may form a parallel path to drive the motor. Similarly, the third brush and the fourth brush may be spaced apart along the second conductor in the direction of travel of the robotic device. The third and fourth brush may also form a parallel path for current driving the motor.
In another embodiment of the present invention, the determined brush failure is transmitted from the robotic device to a control device. This transmission may occur along at least one of the first conductor and the second conductor.
A data storage library is also provided. The library includes storage locations for holding data storage media disposed within the library. At least one rail is located within the library to provide access to the storage locations. At least one conductor for carrying electric current is along each rail. At least one robotic device is mounted to travel along each rail. Each robotic device accesses storage media held in the storage locations. Each robotic device has at least one pair of brushes. Each brush conducts electrical current between the robotic device and the conductor. Electronics within each robotic device determine operating status of each brush based on a measurement of at least one electrical parameter associated with each brush in the pair of brushes.
A mechanism for accessing data storage media in a data storage media devices library by traveling along a rail having an electrical conductor is also provided. A first brush conducts current between the conductor and the mechanism when the first brush is properly operating. A second brush conducts current between the conductor and the mechanism when the second brush is properly operating. Electronics determine a difference signal as the difference in current conducted by the first brush and by the second brush. Control logic determines an operative condition of the first brush and the second brush based on the difference signal.
The above features, and other features and advantages of the present invention are readily apparent from the following detailed descriptions thereof when taken in connection with the accompanying drawings.